A nitride semiconductor light-emitting device includes a plurality of nitride semiconductor layers that are sequentially formed on a substrate. In particular, a nitride-based semiconductor using a nitride such as GaN is widely used for a photoelectric material and an electronic device due to the excellent characteristics thereof, and attracts much attention from those of ordinary skill in the art.
A typical nitride-based semiconductor light-emitting device has a multilayer structure including an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer that are formed on a substrate. The light generated from the active layer is emitted to the outside, and thus the active layer is used as a light source.
In order to obtain light having a wide range of wavelength from the nitride-based semiconductor light-emitting device, the nitride-based semiconductor that is composed of desired elements is used. In particular, in order to emit the light of the ultraviolet region having a wavelength of 320 nm or less, the active layer and the p-type semiconductor layer are formed of an AlGaN element. In the case of p-AlGaN, a hole concentration is theoretically very low, and it is not easy to form an ohmic contact with a metal electrode and to form a p-side electrode. In order to form the p-side electrode, an additional contact layer is formed between the p-type semiconductor layer and the electrode, but the absorption of the light emitted from the active layer saliently degrades efficiency of light extraction of the light emitting-device.